Space Phasor Research Articles

Phase-Modulus Diagram of Instantaneous Current’s Space Phasor as Diagnosis Tool of Induction Motor’s Stator Windings

The paper introduces a new approach for induction motor stator’s windings inter-turns short circuits diagnosis, based on the computer-aided monitoring of the stator Instantaneous Currents Space Phasor (ICSP). Between the stator’s windings short circuits severities and the shape of the permanent geometrical loci of ICSP, as it appears in the polar coordinates modulus-phase, are identified the appropriate correspondences which are used as on-line induction motor fault identifiers. It is shown the new short circuit identifier is insensitive to induction motor load variations. The investigative studies of this new stator windings inter-turns fault identifier are made on a simulated induction motor in Simplorer programming medium.

Power-Loss Ride-Through with Reduced Number of Voltage Sensors in a Cascaded H-Bridge Inverter fed Vector Controlled Induction Motor Drive

Cascaded H-Bridge (CHB) inverter-fed drives are quite popular in high-power industrial applications. However, these drives are extremely sensitive to power supply disturbances on the input grid side, such as voltage sags or short-duration power interruptions that cause the drive to trip on under-voltage protection resulting in production losses. Therefore, it is necessary to employ techniques that improve the resilience of the drive by enabling it to smoothly ‘ride-through’ such short-duration disturbances. The traditional ride-through solutions in CHB drives typically necessitate additional hardware or multiple DC link voltage sensors, which increase the cost and complexity of the system. This paper proposes a simple and cost-effective approach for power-loss ride-through in CHB inverter based vector-controlled induction motor drives. In this method, the kinetic energy stored in the rotating mass is recovered and fed back to the DC-link capacitors to keep all the DC link voltages constant during momentary supply interruptions or voltage sags. The proposed technique works by controlling the voltage space phasor without the need for extra hardware and voltage sensors at the CHB cells. The proposed scheme is experimentally validated on a 30 kW, 7-level CHB inverter based vector controlled induction motor drive.

Investigation of LVRT capability of wind driven dual excited synchronous generator

This paper proposes an effective control technique for low voltage ride through (LVRT) capability in dual excited synchronous generator (DESG) wind turbines. The proposed control technique is dependent on controlling the field circuit parameters. Where the active power is controlled by the field-current space phasor magnitude and the reactive power is controlled by the field-voltage space phasor phase. With the proposed control strategy, the DESG can generate additional reactive power to support grid voltage recovery under grid faults. The DC-link voltage is kept within an acceptable limit since the excess power, due to the power mismatch between the mechanical and armature power is stored in the generator inertia. Using the proposed control strategy, the DESG can enhance the LVRT capability efficiently without using extra protection circuits or any additional control techniques during fault conditions. To test the proposed control method, simulation, and experimental results for a 1.1 kW DESG wind turbine system were obtained.

A Framework Based on Machine Learning for Analytics of Voltage Quality Disturbances

This paper proposes a machine-learning-based framework for voltage quality analytics, where the space phasor model (SPM) of the three-phase voltages before, during, and after the event is applied as input data. The framework proceeds along with three main steps: (a) event extraction, (b) event characterization, and (c) additional information extraction. During the first step, it utilizes a Gaussian-based anomaly detection (GAD) technique to extract the event data from the recording. Principal component analysis (PCA) is adopted during the second step, where it is shown that the principal components correspond to the semi-minor and semi-major axis of the ellipse formed by the SPM. During the third step, these characteristics are interpreted to extract additional information about the underlying cause of the event. The performance of the framework was verified through experiments conducted on datasets containing synthetic and measured power quality events. The results show that the combination of semi-major axis, semi-minor axis, and direction of the major axis forms a sufficient base to characterize, classify, and eventually extract additional information from recorded event data.

Power quality event classification using complex wavelets phasor models and customized convolution neural network

Origin and triggers of power quality (PQ) events must be identified in prior, in order to take preventive steps to enhance power quality. However it is important to identify, localize and classify the PQ events to determine the causes and origins of PQ disturbances. In this paper a novel algorithm is presented to classify voltage variations into six different PQ events considering the space phasor model (SPM) diagrams, dual tree complex wavelet transforms (DTCWT) sub bands and the convolution neural network (CNN) model. The input voltage data is converted into SPM data, the SPM data is transformed using 2D DTCWT into low pass and high pass sub bands which are simultaneously processed by the 2D CNN model to perform classification of PQ events. In the proposed method CNN model based on Google Net is trained to perform classification of PQ events with default configuration as in deep neural network designer in MATLAB environment. The proposed algorithm achieve higher accuracy with reduced training time in classification of events than compared with reported PQ event classification methods.

Active and Reactive Power Control for Dual Excited Synchronous Generator in Wind Applications

This paper presents a dual excited synchronous generator (DESG) as a novel suitable alternative generation system for wind energy conversion systems. A new control strategy was proposed for the DESG wind turbine system. With this control technique, the DESG could be operated as a constant-speed constant-frequency (CSCF) generation system with the benefit of adjusting the reactive power or as a variable-speed constant-frequency (VSCF) generation system with the benefits of simple control methods and lower copper losses. Using the space phasor model of the DESG, a direct relationship between the electromechanical torque and the armature reactive power in terms of the field current space phasor magnitude and the field voltage space phasor angle is provided. The proposed control strategy is based on controlling the field-current space phasor magnitude and the field-voltage space phasor phase angle to regulate the active and reactive powers of the DESG. Simulation results, based on MATLAB/SIMULINK, for a 1.1 kW DESG wind turbine system have been executed to verify the introduced control technique under various operating conditions. Also, experimental studies have been carried out to validate the simulation results using the proposed control algorithm.

Investigations on variable and constant switching frequency hysteresis controller for VSI fed IM drive

In various current controlled-pulse width modulated (CC-PWM) techniques which are extensively employed in high performance drives, hysteresis current control (HCC) offer significant simple implementation and good dynamic response. However, conventional HCC have drawbacks, such as, limit cycle oscillations, overshoot in current error, generation of sub-harmonic components in the current, and non-optimum switching of inverter voltage vectors which can create variable switching frequency. This work proposes a new constant switching current error space phasor (CESP)-based hysteresis controller with a simple online computation of the boundary and phase voltage harmonic spectrum similar to voltage controlled bus clamping PWM (VC-BCPWM)-based VSI fed induction motor drive. The error boundary computed using voltage and current errors in the present sampling interval is used for identifying next vector to be switched. The current controller using CESP approach is simulated using MATLAB Simulink and experimentally verified on 2.2 kW IM drive.

Space vector PWM ‐based current error boundary investigations for three‐level VSI fed induction motor drive

Field oriented control (FOC) of induction motor (IM) powered by a three-level voltage source inverter (3L -VSI) with space vector (SV) based continuous and dis -continuous pulse width modulation (PWM) is presented in this paper. The current error variations in each sector with above-mentioned PWM techniques are monitored and analyzed mathematically. These boundary investigations play a great role in the implementation of Current Error Space Phasor (CESP) based hysteresis current controller (HCC) which incorporates the advantages of a constant switching frequency PWM fed three-level inverter (3LI) into highly dynamic current controlled – voltage source inverter. As a preliminary step, FOC of IM with the conventional space vector PWM and bus clamping PWM (BC30 and BC60) fed 3LI have been simulated using SIMULINK toolbox of MATLAB. Transient analysis of the drive with acceleration, deceleration, and load change studies with different switching schemes are analyzed with d SPACE RTI1103 experimentation on a 2.2 kW three-phase IM drive in detail.

Analysis of Current Error Space Phasor for a Space Vector-Modulated Indirect Matrix Converter

AC motor drives fed from current-controlled power electronic converters are popular on account of their superior steady-state and transient performance. Hysteresis control is a popular current control technique, which needs modifications to compensate for its demerits. Appraisal of current error as a space phasor for implementing the hysteresis controller is one such modification. Current error space phasor (CESP)-based hysteresis controller for voltage source inverters-fed motor drives are capable of achieving superior dynamic performance. With the modified hysteresis current controller, the drive operates at a constant switching frequency and ensures an optimal switching vector selection. This article presents the analysis of CESP for a space vector-modulated indirect matrix converter (IMC). The modified algorithm for space vector modulation of IMC accommodates for the variations in dc-link voltage since CESP is input voltage dependent. The boundary for the hysteresis current controller is calculated from the computed values of CESP. The time-varying nature of the hysteresis boundary ensures a constant switching frequency operation for IMC. Thus, a CESP-based hysteresis controller is proposed for the vector control of the IMC-fed permanent magnet synchronous machine (PMSM) drive. Experimental results are presented for validating the performance of the proposed controller.

New Switching Pattern Based on Space Vectors and Phasors for Quasi Z-Source Inverters

New Switching Pattern Based on Space Vectors and Phasors for Quasi Z-Source Inverters

THE ANALYSIS OF THE THREE-PHASE INDUCTION MOTOR WITH DEEP ROTOR BARS THROUGH NUMERICAL SIMULATIONS UTILIZING A MODIFIED MATHEMATICAL MODEL

The three-phase induction machine mathematical model presented in the paper, is adequate for applying to the deep rotor bars case. The rotor resistance R’r(r), respectively its leakage inductivity L’r(r), depend upon the rotor currents’ frequency fr because of the skin effect. Following the previous considerations, one developed slip dependent analytical expressions of the rotor circuit resistance R’r(s), respectively rotor circuit leakage reactance L’r (s). A modified space phasor based mathematical model of the deep bar induction motor is tested through simulations to assess the motor’s characteristics. The results are in accordance with the literature.

Investigations on STATCOM using current error space phasor based modified hysteresis current controller

Investigations on STATCOM using current error space phasor based modified hysteresis current controller

Behavior of a Pentacle Connected Five-Phase IM Supplied by a Rectangular Voltage

The presented article deals with the steady-state analysis of five-phase Induction Motor (IM), which is supplied by rectangular voltage from a five-leg Voltage Source Inverter (VSI). The new proposed approach is derived from complex Fourier-series using to express inverter terminal voltages. Based on mathematically described inverter output voltages, a formula for VSI output space phasor was derived. Assuming sinusoidal motor winding distribution and on the basis of motor parameters, stator and rotor current space phasors for defined motor load were determined. Finally, the electromagnetic torque ripple waveforms for different IM operation states were investigated.

Fractal Approach Based Simplified and Generalized Sector Detection in Current Error Space Phasor Based Hysteresis Controller Applied to Multilevel Front-End Converters

The current error space phasor (CESP) based hysteresis controller employed for front-end converter requires two (inner and outer) hysteresis bands for vector selection and sector detection, respectively. As a result of this, the CESP moves out of the fixed (hexagonal) inner boundary many times in one fundamental cycle (and touches outer hysteresis band) to detect appropriate sector. This distorts the supply current waveform and increases the implementation complexity. To provide effective solution to the said issue, in this article, a fractal approach with a triangularization technique is proposed and analyzed to eliminate the outer hysteresis band and lookup table for sector change detection. The novelty proposed in this article is the integration of the fractal approach to CESP-based hysteresis controller, which reduces the complexity of the implementation of CESP-based hysteresis controller for any general multilevel front-end converter. The detailed analysis of the proposed technique for sector detections is presented considering the voltage space phasor structure of three-level and five-level converters. A generalized flowchart for any multilevel converter employing CESP-based hysteresis controller with proposed sector detection technique is developed and presented. Laboratory prototype is developed for a three-level flying capacitor front-end converter with an effective capacitor voltage balancing scheme. The experimental results are presented to validate the effectiveness of the proposed current controller in terms of unity power factor and low harmonic distortion in the line current under various practical conditions.

Analysis of Multiaxis Current Controller for Power System Friendly Front-End Converter Employing Two-Level and Three-Level Topologies

It is highly essential to develop a control technique that can be applied to conventional two-level as well as high-power multilevel front-end converters (FECs). Multiaxis current controlled, unity power factor (PF), regenerative FEC is described in this article. Current error space phasor is controlled by multiaxis current monitoring and its movement is confined within the prescribed hexagonal boundary. It is shown that the needed information on sector change detection can be derived from instantaneous values of supply voltages for the two-level FECs. However, similar approach cannot be extended for three-level FECs. Hence, sector change detection technique employing additional outer hysteresis band is proposed. With the help of experimental results, for steady state and dynamic conditions of FEC, it is demonstrated that the proposed current-controlled technique is equally applicable to two-level and three-level FECs. A three-level flying capacitor topology is considered, where voltage balancing of flying capacitors is guaranteed by effective utilization of redundant switching states. Results clearly depict the power system friendly nature of the presented scheme, i.e., unity PF, low total-harmonic distortion in supply current, good load and line regulations, and capacitor voltage balancing with regenerative capability of the converter. All the schemes are implemented on OPAL-RT hardware-in-loop platform.

Online Boundary Computation Using Sampled Voltage Reference for Bus Clamping PWM-Based Hysteresis-Controlled VSI-Fed IM Drive

A current error space phasor based hysteresis current controller (HCC) with online computation of the current error boundaries using estimated sampled voltage references (SVR) for a two-level voltage source inverter (VSI) fed induction motor (IM) drive is proposed in this article. The space vector based current error of a two-level VSI-fed IM is monitored to keep the current error within the precalculated boundaries. The boundaries are computed knowing voltage error vector estimated from the current error information along α and β axes of IM. Vector selection logic is deduced to extract the features of voltage-controlled (VC) –30° and 60° bus clamping (BC) space vector pulsewidth modulation (SVPWM) based VSI-fed IM drive. The proposed HCC produces phase voltage harmonic spectrum and current error trajectories similar to that of a constant switching frequency—VC-BCSVPWM drive. It ensures adjacent voltage vector switching and retains all inherent advantages of a conventional HCC such as fast current control and has got a simpler controller implementation. A simulation model using MATLAB/Simulink is developed and analyzed over a wide speed range and experimentally validated using a dSPACE controller board on a 2.2 kW, 415 V, 3ϕ IM drive.

Dual <inline-formula> <tex-math notation="LaTeX">$P$</tex-math> </inline-formula>-<inline-formula> <tex-math notation="LaTeX">$Q$</tex-math> </inline-formula> Theory Based Energy-Optimized Dynamic Voltage Restorer for Power Quality Improvement in a Distribution System

This paper deals with the protection of critical loads from voltage-related power quality issues using a dynamic voltage restorer (DVR). A generalized control algorithm based on instantaneous space phasor and dual $P$ - $Q$ theory has been proposed to generate the instantaneous reference voltages to compensate the load voltages with direct power flow control. The proposed algorithm adapts energy-optimized series voltage compensation, which results in a reduction of energy storage requirement. The proposed DVR control scheme can support the load from voltage-related power quality issues irrespective of the load current profile. Each leg of the three-phase three-leg split capacitor inverter is used to inject series compensation voltage in respective phases of the system. Model-based computer simulation studies and real-time experimental results validate the effectiveness of the proposed control algorithm.

Three-phase power transformer modelling in AC/DC traction substations

Three-phase power transformer is one of the most important elements in the electric power systems, and it plays a significant role in terms of energy savings. Since the efficiency standards can be expressed in terms of electrical efficiency, in an attempt to improve the transformer efficiency, in this study an enhancement of three-phase power transformer modelling with space phasors is presented. There are established the equations with space phasors of the three-phase transformer with symmetrical compact core. This equations system can be used to analyze the dynamic regimes of three-phase transformers. In this paper have been analyzed some aspects of three-phase power transformer operation in a AC/DC traction substation.

DETECCIÓN MULTICRITERIO DE FALLOS DE UN MOTOR BLDC (BRUSHLESS DIRECT CURRENT)

This work presents a multiple criteria approach for stator fault detection (FD) in an in-wheel brushless DC (BLDC) motor for electric vehicles. The detection of inter-turn short circuits in the stator windings of the BLDC is studied. The fault detection scheme is performed based on the instantaneous space phasor (ISP). The fault signature (residual) is built using the fast Fourier transform (FFT) and discrete wavelet transform (DWT). An experimental setup comprising a modified in-wheel BLDC was used to validate this approach. The results of signal processing based FD are verified by an analysis made with thermographic techniques. Key Words: in-wheel BLDC motor, fault detection, FFT, DWT, entropy, infrared image, electric vehicle.

Dynamic Analysis of Multi-machine Power Systems Facing Symmetrical and Asymmetrical Simultaneous Faults

This paper presents a new method for dynamic analysis of multi-machine power systems due to symmetrical and asymmetrical simultaneous faults. The method uses the time-varying-quasi-stationary space phasors-based sequence networks for dynamic analysis of power systems. In this paper, a new technique is proposed based on the concept of space phasors, which allows the modelling of synchronous machines as current source space phasors in the sequence networks. Therefore, the admittance-type representation of sequence networks is used for dynamic analysis of power systems facing simultaneous faults. In transient stability programs, the three-phase representation of the networks is used for dynamic analysis of faulty power systems in balanced or unbalanced conditions. But, the proposed method uses the positive-sequence network in the pre-fault and post-fault conditions and uses a combination of sequence networks during the fault time that enhance the efficiency of the simulations. Moreover, the proposed method is capable of considering the negative-sequence network dynamics in power systems dynamic analysis. Judgment of results between the proposed method and two of the commercial software has been accomplished for a single-machine-infinite-bus system, which validates the method. In addition, the method has been tested for the 30-busbar IEEE power system as a template of a standard power system. Simulation results show the effectiveness of the proposed method. The content of this paper should be of interest to engineers for power system transient stability, dynamic stability and protection.